1. Field of the Invention
This invention relates to novel dyestuff compositions containing a plurality of dye cakes and a dispersant having retarding properties. More particularly, this invention relates to dyestuff compositions containing multi-dispersed dyes of various colors, in an aqueous solution, dispersed and retarded with the reaction product of a sulfonated lignin and a water-soluble salt.
2. The Prior Art
Many reactants have been used to modify the lignin by-product of woodpulping in order to formulate particular dyestuffs of certain characteristics needed in particular dyeing operations. By way of illustration, U.S. Pat. No. 3,505,243 to J. C. Steinberg et al. describes a sulfite lignin dispersant. U.S. Pat. No. 3,672,817 to S. I. Falkehag et al describes another modified sulfonated lignin dye dispersant. These patents cited show the state of the art, and are not intended to be all inclusive of lignin modifications as neither teach modification with magnesium sulfate.
Dyestuff compositions comprise, for the most part, a dye cake, i.e., disperse dyes or vat dyes, and a dispersant. There dyestuff compositions are widely used to color both synthetic and natural fibers. The various commercially available dye dispersants, that are used to disperse dye cake, vary widely depending upon the method of dyeing, the chemical composition of the cake, and the fabric being dyed. However, in general, various qualifications can be asserted for the dispersants in the dyestuff. In the dyestuff composition, the dispersant serves three basic functions.
1. It assists in reducing the dyestuff to a fine particle size. PA1 2. It maintains the fine particle size in a dispersed medium. PA1 3. It is used as an inexpensive diluent of the dye cake.
Generally, dye dispersants, used for dyestuffs, have been of two major types, sulfonated lignins from the wood pulping industry via the sulfite or kraft processes, and sulfonated napthalene products from the petroleum industry. Both of these dispersant types have found applicaton in one or more areas of dye dispersion; however, each dispersant possesses one or more undesirable properties.
Disadvantages of certain of these dispersants, whether they are sulfonated lignins or sulfonated napthalene products, include uneven dyeing. Uneven dyeing is the result of one of the dyes in a multi-color dyestuff going into solution at a greater rate than the other color dye cakes. An economically feasible solution to the uneven dyeing phenomena has not been commercially available to the dyeing industry. Uneven dyeing can occur on cellulosic and nitrogenous fibers, such as cotton, nylon and wool, as well as polyester fibers. Various products have been offered by dry cake manufacturers and dispersant manufacturers as a result of the demands of the dye industry. However, to this date, none of the products have maintained stable reproducible results sufficient to remedy the ever prevalent uneven dyeing problem. It is this property where many dye dispersants begin to fail. Other disadvantages include poor heat stability, fiber staining, as well as fiber streaking, and a tendency to stabilize foams. While the first consideration is given to how effectively a product functions as a dispersant, the second is given to stability of the dispersion under heat and pressure. Lastly, foam stabilization properties of dyestuff composition are troublesome for several reasons. First, in ball milling or grinding, in general, foam creates cleaning problems by frothing out of dispersion tanks and by building up foam within ball mills which generally slows the grinding process. Spray drying liquor with considerable foam causes a fluctuation of the temperature within the dryer. As many dyes are acutely sensitive to heat, this can cause deterioraton of these particular dyestuffs.
The advantages that the sulfonated lignin dye retarding dispersant of this invention possess over other dye dispersants include the ability to retard at least one of the dyes in a multi-color dyestuff composition to the extent necessary for levelling to be effecuated in the dye bath. Although the exact mechanism of the foresaid retarding action is not entirely understood, the results are readily reproducible with normal scientific accuracy in the vat dye industry. The resulting dyestuff, from the interaction of the dispersed dye cakes and the dispersant having retarding properties produces a level application of the dyes in the vat dyeing process. This levelling effect is the industry's terminology for the condition of the dye vat which produces an evenly dyed fabric, i.e., maintaining a constant shade of color at all points in the dyeing process when a mixture of two or more colors are being used to achieve a desired shade of color. Furthermore, it eliminates unevenly dyed fabric at the creases in the materials. The condition is much desired by the dyer for the accomplishment of a superior dye job. The condition is economically demanded of the industry due to the highly competitive field and low profit margin of the dye business. Another advantage of the retarding dispersants of this invention is that they have low foam stabilization properties, and render excellent dispersion qualities to the soluble dye cakes.
It is therefore, the general object of this invention to provide a dyestuff composition containing a selectively sulfonated lignin dye dispersant having retarding properties that are capable of providing the necessary levelling in a multi-color dye process. Furthermore, it is the object of this invention to satisfactorily disperse the dye, maintaining a superior antifoaming quality and overcoming to a large degree the objections of the prior art dyestuff compositions. Another object of the present invention is to provide a dyestuff composition containing a dispersant comprising a plurality of dyes and a dispersant which is the reaction product of a sulfonated lignin and a water-soluble magnesium salt.
Further objects, features and advantages of this invention will be evident from the following detailed description of the preferred embodiment.